Easy Built Lite Tissue in Dark or Medium Navy would do the trick at 60 cents a sheet. Acrylic is the only way to go, but I have never tried putting it directly on the tissue and have no idea what it would do. I usually apply two coats of clear dope thinned to 50% with thinner and it works well with Acrylics. Good luck!

Note: Elmers White Glue thinned 50/50 (as a substitute for dope) as a sealer will work quite well with acrylic. You might get a little sag from the glue and/or the acrylics but, it will tighten back up as it dries. I use this exclusively....Luck

I think that you'll probably need something to seal the pores of the tissue before you paint, sealing is the primary purpose of a dope. If you don't want to use cellulose dope etc then John's suggestion is the best alternative. A friend of mine used it and it turned out very well.

BTW, I use non shrinking cellulose dope ie all the shrinking is done with water before I apply dope, IMO Shrinking dope is a no no on small delicate models as it will distort the structure

Try Krylon Crystal Clear artist fixative, #1303 or 1305, to fix the tissue instead of dope. It is less toxic than dope but should still be sprayed outside. A couple of misted coats should do to seal the tissue. I have models that I built in 2004 using Krylon that are still flyable.

Airbrushing acrylic paints or acrylic artist's ink over Krylon works very well. Krylon fixative is water resistant, not waterproof as dope, so the large load of water carried by the acrylics will cause tissue to sag after spraying but it will tighten back up again in a few minutes to hours depending on the temperature and humidity. Obviously, you have to let it completely dry between colors and changing masking. You can mask with airbrush frisket or Guillow's tissue sprayed with three or four coats of Krylon then cut as masking and applied with a repositionable glue stick (Post-It note glue).

This Guillow's 500 series Spitfire is an example of a model done this way,

If you put a water slide decal on undoped tissue the tissue will shrink under the decal when the water dries and the decal will wrinkle. Unfortunately, since Krylon is water resistant, not waterproof, the same kind of thing will happen if you put a large decal on a Kryloned surface. In this case the tissue sags under the water when the decal is applied then shrinks tight again when dry wrinkling the decal.

I scan my decals and print them on tissue, then cut them out and apply them with a Uhu glue stick. The markings on the Spitfire are "tissuecals" not decals.